Petroleum middle distillate fuel with improved low temperature flowability

ABSTRACT

The low temperature flowability of a middle distillate petroleum fuel boiling within the range of about 250* and about 700*F. at atmospheric pressure is improved by adding to the fuel a combination of a microcrystalline petroleum wax and a wax modifying additive which comprises either a polymer containing halogenated polymethylene segments or an N-aliphatic hydrocarbyl succinamic acid or a derivative thereof. The invention is particularly advantageous in improving the flow of a diesel fuel through a fine filter at low temperatures.

United States Patent r1 1 Feldman 1 Nov. 12, 1974 [75] Inventor: Nicholas Feldman,Woodbridge,

[73] Assignee: Exxson Research and Engineering Company, Linden, NJ.

[22] Filed: June 4, 1973 [21] Appl. No.: 366,537

Related 1.1.8. Application Data [63] Continuation-impart of Ser. No. 157,615, June 28,

1971, abandoned.

[52] US. Cl 44/62, 44/63, 44/70,

44/71, 44/72 [51] Int. Cl C101 1/22 [58] Field of Search 44/62, 63, 70, 71, 72

[56] References Cited UNITED STATES PATENTS 3,250,599 5/1966 Kirk et a1 44/62 3,444,082 5/1969 Kaulsky 44/62 3,645,704 2/1972 Burkard... 44/62 3,676,089 7/1972 Morris 44/62 3,288,577 11/1966 Palinkin et al.. 44/62 3,337,313 8/1967 Otto 44/62 Primary ExaminerDaniel E. Wyman Assistant ExaminerMrs. Y. H. Smith Attorney, Agent, or Firm-Byron O. Dimmick [57] ABSTRACT The low temperature flowability of a middle distillate petroleum fuel boiling within the range of about 250 and about 700F. at atmospheric pressure is improved by adding to the fuel a combinationof a m'icrocrystalline petroleum wax and a wax modifying additive which comprises either a polymer containing halogenated polymethylene segments or an N-aliphatic hydrocarbyl succinamic acid or a derivative thereof. The invention is particularly advantageous in improving the flow of a diesel fuel through a fine filter at low temperatures. 4 i

9 Claims, No Drawings PETROLEUM MIDDLE DISTILLATE FUEL WITH IMPROVED'LOW TEMPERATURE FLOWABILITY CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 157,615, filed June 28, 1971 now abandoned.

FIELD OF THE INVENTION Heating oils and other middle distillate petroleum fuels, e.g., diesel fuels, contain normal paraffin hydrocarbon waxes which, at low temperatures, tend to precipitate in large crystals in such a way as to set up a gel structure which causes the fuel to lose its fluidity. The lowest temperature at which the fuel will still flow is generally known as the pour point. When the fuel temperature goes below the pour point and the fuel is no longer freely flowable, difficulty arises in transporting the fuel through flow lines and pumps, as for example when attempting to transfer the fuel from one storage vessel to another by gravity or under pump pressure or when attempting to feed the fuel to a burner. Additionally, the wax crystals that have come out of solution tend to plug fuel lines, screens and filters. This problem has been well recognized in the past and various additives have been suggested for depressing the pour point of the fuel oil. One function of such pour point depressants has been to change the natureof the crystals that precipitate from the fuel oil, thereby reducing the tendency of the wax crystals to set into a gel. Small size crystals are desirable so that the precipitated wax will not clog the fine mesh screens that are provided in fuel transportation, storage, and dispensing equipment. The pour point of a petroleum fuel oil is not the only measure of the flowabilityof that fuel at low temperatures;

an equally important factor is the low temperature filterability of the fuel, i.e., its ability to pass through a filter. It is thus desirable to obtain not only fuel oilswith low pour points, but also oils that will form small wax crystals so that the clogging of filters will not impair the flow of the fuel at low operating temperatures.

DESCRIPTION OF THE PRIOR ART It is known in the prior art to employ various polymeric and copolymeric materials as pour point depressants for wax-containing petroleum fractions. Chlorinated polymers of ethylene are taught for this purpose in U.S. Pat. No. 3,337,313. The use of an alkenyl succinamic acid that is disubstituted on the nitrogen atom or of the amine salts of such acids, and the use of such acids or their salts in combination with a low molecular weight ethylene-olefin copolymer are taught in U.S. Pat. No. 3,444,082. The use of a combination of a petroleum microcrystalline wax and certain pour point depressant additives including copolymers of olefins and styrene, condensation products of naphthalene and sperm oil, or copolymers of ethylene and vinyl acetate is taught in U.S. Pat. Nos. 3,250,599 and 3,288,577. The surprisingly effective combinations of microcrystalline wax with the additives used in the present invention are not disclosed in the prior art.

DESCRIPTION OF THE INVENTION In copending application Ser. No. 157,615 of which the present application is a Continuation-ln-Part, it is taught that the low temperature flow properties of a middle distillate fuel can be improved by incorporating a combination of an amorphous hydrocarbon fraction, substantially free of normal paraffinic hydrocarbons, and either a polymer containing halogenated polymethylene segments or an N-aliphatic hydrocarbyl succinamic acid or a derivative thereof. It has now been surprisingly found that the low temperature flow properties of a petroleum middle distillate fuel oil can be improved by incorporating, in combination with either the above-described halogenated polymer or the N- aliphatic hydrocarbyl succinamic acid, a small quantity of a microcrystalline wax that contains appreciable quantities of normal paraffinic hydrocarbons. More specifically there are added to a waxy middle distillate petroleum fuel from about 0.05 to about 2.5 wt. percent of amicrocrystalline wax and from about 0.005 to about 0.5 wt. percent of a fuel-soluble additive component selected from the group consisting of a halogenated ethylene-containing polymer with a halogen content of from about 1 to 40 wt. percent and an alkenyl succinamic acid material, both of which are more fully described below.

The distillate fuel oils that can be improved by this invention include those having atmospheric boiling ranges within the limits of about 250F. to about 700F. The distillate fuel oil can comprise straight run or virgin gas oil or cracked gas oil or a blend in any proportion of straight run and thermally and/or catalytically cracked distillates.

The most common petroleum middle distillate fuels are kerosene, diesel fuels, jet fuels and heating oils. Since jet fuels are normally refined to very low pour points, there will generally be no need to apply the present invention to such fuels. The low temperature flow problem is most usually encountered with diesel fuels and with heating oils. A representative heating oil specification calls for a 10 percent distillation point no higher than about 440F., a 50 percent point no higher than about 520F., and a percent point of at least 540F. and no higher than about 640F. to 650F., although some specifications set the 90 percent point as high as 675F. Heating oils are preferably made of a blend of virgin distillate, e.g., gas oil, naphtha, etc., and cracked distillates, e.g., catalytic cycle stock. This invention is particularly applicable to use with diesel fuels, which must be capable of passing through very fine filters at low temperatures. A representative specification for a diesel fuel includes a minimum flash point of F. and 90 percent distillation point between 540F. and 640F. (See ASTM Designations D396 and D-975).

The microcrystalline waxes employed in the present invention are obtained from residual petroleum oils. Such microcrystalline waxes are characterized by very minute crystalline forms, considerably finer than those of paraffin wax, and melt in the range of from about to about F., and thus have melting points appreciably higher than the melting points of the ordinary paraffin waxes. The average molecular weights of microcrystalline waxes generally range from about 490 to about 800 as contrasted with the molecular weights of paraffin waxes which are in the range of about 350 to 420. Microcrystalline waxes will generally have a small turn containing larger amounts of oil, e.g., 5 to 30 percent oil.

As already stated, one type of pour point depressant additive that is employed in conjunction with a microcrystalline wax in the practice of the present invention comprises an oil-soluble polymer containing halogenated polymethylene segments. This polymer is an oil soluble, halogenated, predominantly hydrocarbon material having an average molecular weight of from about 200 to about 500,000, more preferably from about 500 to 50,000. Most advantageously molecular weights are within the range of about 500 and 10,000. The average molecular weights of the polymers may be conveniently determined by means of an ebullioscope or by means of an osmometer.

The polymers that are halogenated for use in this invention are polymers of ethylene or copolymers of ethylene with other monoolefins of from 3 to 6 carbon atoms, although higher olefins in the copolymers are not excluded. Preferably, the polymer or copolymer contains from 5 to about 100 wt. percent of ethylene.

Preferably the halogenated polymers used in this invention are chlorinated polymers. The chlorination produces chlorine substituents on the polymer chain. The chlorination can be carried out by any one of several procedures, the chlorination progressing until the desired content of chlorine is reached. The optimum chlorine contents will be dependent somewhat upon the particular polymer being chlorinated. Usually the chlorinated materials will contain from about 0.2 to about 40 percent by weight, preferably 1 to 35 percent by weight and most preferably 1.5 to about 25 wt. percent of chlorine.

In one process for chlorinating a polymer, chlorine is bubbled through the molten polymer under temperature conditions within the range of about 150 and 400F. A second process involves bubbling chlorine through the polymer suspended in an inert solvent, such as carbon tetrachloride (or other chlorinated methanes, chlorinated ethanes, and the like) under temperature conditions of at least 75F. The rate of reaction may be accelerated by using an actinic light source. In a third process chlorine is bubbled through an aqueous suspension of the polymer. The first two.

processes are preferred since it is believed that in their use the chlorine contacts a greater portion of the inner polymer chain. It is to be understood that the chlorine addition includes the use of known chlorinating compounds such as sulfuryl chloride, oxalyl chloride, phosgene and the like.

In general, the polymers and techniques of chlorination most preferred are similar to those used in and described in U.S. Pat. No. 3,337,313, which is incorporated herein by reference in its entirety. One significant difference in the description in that patent is that polymers made by the Ziegler process are equally applicable for use in the present composition. Descriptions of polymerizations and polymers resulting from Ziegler type catalysts suitable for use in thisinvention will be found in the profuse publications in the art. U.S. Pat. No. 3,389,087 and U.S. Pat. No. 3,474,157 are representative examples of these.

As stated earlier, a second type of pour point depressant additive employed with the microcrystalline wax in the practice of the present invention comprises an aliphatic hydrocarbyl succinamic acid or a derivative thereof. The hydrocarbyl succinamic acid can for the most part be represented bylhe follojfing formula:

R CH COX ll. CH 001! wherein N has its normal meaning of nitrogen and Y and Y are aliphatic hydrocarbyl groups of from F4 to 40 carbon atoms, more usually of from 15 to 30 carbon atoms, the total of Y plus Y being from about 30 to 52 carbon atoms, more usually from 32 to 48 carbon atoms, and, preferably, from 32 to 40 carbon atoms.

Y and Y can be aliphatically saturated or aliphatically unsaturated, generally free of acetylenic unsaturation (i.e., either alkyl or alkenyl). There can be from one to two sites of olefinic unsaturation. Y and Y may be the same or different and may be straight chain or branched chain, preferably straight chain. The branches will normally be not greater than 1 carbon atom, i.e., methyl. The position of attachment to nitrogen can be at a terminal or at an internal carbon atom.

As is evidenced from the above formula, it is not important which position the alkyl or alkenyl group has in relation to the carboxamide or carboxyl group. Because of the bulky nature of the amine, the usual method of preparation through the succinic anhydride will provide the alkenyl group ,6 to the carboxamideas the major product. To the extent that this is the more easily accessible derivative, this derivative is preferred. However, as far as operability is concerned, either isomer or a mixture of the two isomers can be used. lndividual compounds or mixtures of compounds may be used. Mixtures of different C- and/or N-substituents, both as to homologs and isomers, will frequently be employed when the individual precursors to the succinamic'acid product are not readily available. Illustrative succinamic acids include: N,N-dihexadecyl hexadecylsuccinamic acid; N-hexadecyl, N-octadecyl octadecylsuccinamic acid; N,N-dihexadecenyl, C -alkenylsuccinamic acid; N-hexadecenyl, 1 N eicosenyl octadecylsuccinamic acid; N,N- dioctadecenyl C -alkenylsuccinamic acid; etc.

As indicated previously, the succinamic acid may be used as its amine salt, preferably as a mixture of acid and amine salt. The acid or the amine salt or mixtures thereof can be represented by the following formula:

n ea 00x n -cwr wherein R is as previously defined, and one of the X and X? is -NYY wherein Y and Y are as previously defined. The other of X and X is of the formula:

wherein Y and Y may be hydrogen, aliphatic hydrocarbon of from 1 to 30 carbon atoms or oxaliphatic hydrocarbon of from 3 to 30 carbon atoms, there being 1 ethereal oxygen atom present in the radical bonded to nitrogen at least ,8 to the nitrogen atom). Y and Y may be taken together to form a heterocyclic ring of from 5 to 7 members having nitrogen and oxygen as the only heteromembers. The value of n varies from 0 to 1, preferably from 0.1 to 0.9; that is, from 10 to 90 mole percent of the succinamic acid present is in the form of its salt.

The aliphatic hydrocarbon groups are preferably saturated and if unsaturated will usually have no more than 2 sites of ethylenic unsaturation. The total number of carbon atoms for HNY Y will be from 0 to 60, usually l to 40.

The groups indicated for Y and Y may also be used for Y and Y Usually, where an amine other than the one used to prepare the succinamic acid is used to form the salt, as will be explained subsequently, there will be a mixture of salts; both the added amine and the secondary amine employed to prepare the succinamic acid will be involved in salt formation. Primary amines may be used as well as secondary amines to form the salt. Illustrative amines that can be used to form salts include di-sec-butyl amine, heptyl amine, dodecyl amine, octadecyl amine, tert-butyl amine, morpholine, diethyl amine, methoxybutylamine, methoxyhexylamine, etc.

The hydrocarbyl succinamic acids of this invention are readily prepared by reacting an alkyl or alkenyl succinic anhydride with the desired secondary amine at a temperature in the range of about 150 to 250F. in approximately equimolar amounts, either neat or in the presence of an inert solvent. The time for the reaction is generally in the range of minutes to 1 hour. This reaction is well known in the art and does not require extensive discussion here.

The alkyl or alkenyl succinic anhydride that is used may be an individual compound or may comprise mixtures of compounds; that is, various alkyl or alkenyl groups of differing number of carbon atoms or different positions of attachment to the succinic anhydride group may be used. Alternatively, a single isomer may be used. Since mixtures are generally more readily available, to that degree they are preferred. Frequently, use will be made of mixtures of aliphatic hydrocarbyl substituted succinic anhydrides wherein no single homolog is present in amount greater than 25 mole percent, each homolog being present in at least 5 mole percent.

Various secondary amines, both those having the same aliphatichydrocarbon groups and those having different aliphatic hydrocarbon groups, can be used in making the succinamic acid. Either alkyl or alkenyl substituents may be present on the nitrogen, each having at least 14 carbon atoms. The range of difference between the two aliphatic hydrocarbon groups bonded at the nitrogen is not critical, but will generally be fewer than 8 carbon atoms, more usually fewer than 6 carbon atoms. For the most part, the aliphatic hydrocarbon groups will be straight chain, i.e., normal, with the amino nitrogen bonded either to internal or to terminal carbon atoms.

It has been found that when using approximately a 1:1 mole ratio of amine to succinic anhydride, depending on the reaction conditions, a significant amount of amine may be unreacted and remain to form the salt of the succinamic acid that is formed. In some instances,

as much as 30 percent of the amine may remain unreacted, forming a significant amount of salt. Thus, the salt will frequently be from 10 to 30 mole percent of the total succinamic acid present.

Also, in situations where significant amounts of water are present during the course of the reaction, the water may react with a succinic anhydride to form succinic acid. If the temperature is not high enough to regenerate the succinic anhydride, the succinic acid will probably remain unreacted or form the amine salt with available unreated amine. Therefore, the mixtures of amic acid salts may be conveniently prepared merely by using a 1:1 mole ratio of amine to succinic anhydride, and not attempting to drive the reaction to completion, or up to a mole excess of amine.

The amine salts are readily prepared by adding the amine to the succinamic acid either as such or in an inert solvent. Mild heating may facilitate the reaction.

An optional aspect of this invention is to use, in combination with the succinamic acid component, one or more olefin polymers, particularly ethylene-olefin copolymers of from about 1,000 to 100,000 molecular weight, preferably from about 1500 to 20,000 molecular weightwherein the mole ratio of ethylene to its comonomer is from about 6:1 to about 12:1.

The polymers employed in this aspect of the invention should have polyethylene segments in the polymer approximating the chain length of the wax. That is, the polyethylene segments should have from about 6 to 30 monomers on the average.

Thus the major function of the other monomer is to act as a divider between the polyethylene segments. For this reason, various monomers may be used that can be conveniently copolymerized with the ethylene. Such olefins include hydrocarbon terminal olefins and mixtures thereof of from about 3 to 30 carbon atoms, more usually of from about ID to 30 carbon atoms and various heteroatom-containing addition polymerizable terminal olefins such as the acrylates, methacrylates, vinyl ethers, vinyl ketones, vinyl esters, dicarboxylic acids and esters, etc.

The hydrocarbon olefins that find use in the copolymers will have the following formula:

wherein W is hydrogen or methyl and Z is hydrocarbon of from 1 to 30 carbon atoms, more usually alkyl, Z is free of aliphatic unsaturation.

For the most part, the heteroatom-containing olefins will have the following formula:

where W is hydrogen, alkyl of from I to 3 carbon atoms or Z, and Z is hydrocarbyloxycarbonyl where Q has from 1 to 20 carbon atoms and is aliphatically saturated hydrocarbyl, hydrocarbyloxy, acyloxy (QCO or hydrocarbyl carbonyl. Z is free of aliphatic unsaturation.

The preferred Z is acyloxy or hydrocarbyloxycarbonyl. The heteroatom-containing monomer will generally be of from 4 to 24 carbon atoms, more usually of from 4 to 20 carbon atoms, have from 1 to 2 oxygen heteroatoms, and have only one site of olefinic unsaturation as its only aliphatic unsaturation.

The method of preparation of the polymer or copolymer used with the succinamic acid component is not critical to this invention. Any convenient method for obtaining polymers of the desired molecular weight may be used. In preparing the hydrocarbon copolymers, usually nonstereospecific catalysts will be employed. Illustrative of such catalysts are triethylaluminum with vanadium oxychloride or titanium tetrachloride. These catalysts are in the category known as Ziegler-type catalysts. Alternatively, free radical, high pressure polymerizations may also be used.

The ratio of alkenyl succinamic acid component to other polymers will generally be about 0.25 to parts of the succinamic acid or salt to 1 part of the polymer, more usually from about 2 to 8 parts of the succinamic acid component per part of polymer, preferably 3 to 6 parts of acid component to polymer.

The fuel compositions of this invention will contain from about 0.01 to about 2.5 wt. percent of the microcrystalline wax and from about 0.005 to about 0.5 wt. percent of the other additive, i.e., the halogenated ethylene-containing polymer or the hydrocarbyl succinamic acid or its amine salt or combination of hydrocar'byl succinamic acid component and olefin polymer or copolymer as hereinabove described. The weight ratio of the two components in the combination can range from about 20:1 to 1:20, more usually from about 10:] to 1:10 and most preferably from about 5:1 to 1:5. Although the separate components can be blended directly into the fuel by simple mixing it will frequently be found desirable to prepare a concentrate by first associating each component with a separate solvent or by dissolving the two components in a common solvent. For example, heavy solvent naphtha or a similar solvent or aromatic character can be employed. The concentrates can contain from 5 to 60 wt. percent of total additives.

This invention will be further understood when reference is made to the following examples which include preferred embodiments.

EXAMPLE 1 Fuel oil blends were prepared using a middle distillate fuel oil consisting of 75 vol. percent of cracked distillates having a final boiling point of 665F. and 25 vol. percent of straight run heavy virgin naphtha, the fuel oil having a cloud point of +12F. and an API gravity of 30.1 at 60F. To separate portions of this fuel oil there were added different percentage concentrations of a microcrystalline wax, and to other portions there were added different percentage concentrations of an alkenyl succinamic acid derivative, or a halogenated substantially ethylene-containing polymer. To still other portions of the fuel oil there were added both the microcrystalline wax and either the alkenyl succinamic acid derivative or the halogenated ethylene-containing polymer.

the microcrystalline wax used in the above blends had a molecular weight of 634, a melting point of 167F., and a normal paraffin content of 22.6 percent. The halogenated polymer was a substantially ethylenecontaining polymer having a number average molecular weight of 2,500 and a chlorine content of 21 weight percent and was otherwise identified as Tolad 33 obtained from the Tretolite Division of 'Petrolite Company. The succinamic acid derivative was a material known as OFA-4l0 supplied by the Chevron Chemical Company. The preparation of such succinamic acid is described in Example 1 of US. Pat. No. 3,444,082. The Tolad was in the form of a 50 wt. percent concentrate in a hydrocarbon oil, and the OFA-4l0 was in the form of about 70 wt. percent concentrate in a hydrocarbon oil.

Each of the fuel oil blends as well as a sample of the fuel oil without additives was subjected to a low temperature flow test known as a low temperature screen test, in which a 200 ml. sample of the oil is cooled at a controlled rate of 4F. per hour until a temperature of l0F. is reached, this being the temperature at which the flow test is conducted. The oil at the test temperature is caused to flow from an upper compartment of the tester into a lower compartment of the tester, all held at the test temperature, the oil passing by gravity through a 30 mesh screen of l centimeter diameter for 25 seconds. The volume percentage of oil that has flowed through the screen at the end of this time is then measured. If more than 90 volume percent of the oil has gone through the screen at the end of the 25 seconds, the oil is considered to have passed the test.

The compositions of the various heating oil blends tested and the test results obtained in the low temperature flow test are given in Table l which follows. The weight percentages of the added materials are based on the total composition in each instance. The stated 1 amount of second additive in each case is that of the concentrate of the respective additive and not of active The data in Table I show that while the alkenyl succinamic acid derivative and the halogenated ethylenecontaining polymer each improved the low temperature properties of the heating oil to some extent, the microcrystalline wax gave no improvement in low temperature flow, and yet the combinations of microcrystalline wax and either of the other additives were very effective in improving the low temperature flow properties of the heating oil.

EXAMPLE 2 The additive combinations of the present invention were also tested in a diesel fuel wherein the requirements are more severe than for a heating oil since a diesel fuel must pass through much finer screens or filters. Blends were prepared in a diesel fuel comprising 45 percent catalytically cracked and 55 percent virgin distillates. The diesel fuel had an atmospheric boiling range of 396 to 646F., a cloud point of +2F. and an API gravity of 34.2 at 60F. The diesel fuel and blends containing the additives were subjected to a low temperature filterability test in which 200 ml. of the fuel is cooled at a rate of 4F. per hour until a temperature of either 5F. or 1 F. is reached, these being the temperatures at which the flow test is conducted. The cold diesel fuel is then caused to flow through a 325 mesh screen of l centimeter diameter using an applied vacuum of 4 inches of mercury, and the percentage of the fuel flowing through the screen in 25 seconds is determined.

The compositions of the diesel fuel blends tested and the test results obtained are given in Table II which follows. The microcrystalline wax used was the same as that in Example I.

TABLE II Percent Diesel Fuel Through 325 Mesh Screen in 25 Sec.

It will be noted that the succinamic acid additive improved low temperature flow properties to some extent at F. but did not improve the low temperature flow at l0F., while the microcrystalline wax did not improve the low temperature flow properties at all, and yet the combination of the succinamic acid derivative and the microcrystalline wax gave a 100 percent recov: ery of fuel at both 5F. and -l0F. The combination of 0.1 percent of the chlorinated ethylene polymer and 0.2 percent of microcrystalline wax gave a slightly better improvement than with 1% times as much of the chlorinated polymer alone.

COMPARATIVE EXAMPLE In the same manner as in Example 2, blends were prepared with the same diesel fuel base as in that example. In one blend there was used a combination of the microwax with a copolymer, of about 2,200 number average molecular weight, of about 60 wt. percent ethylene and 40 wt. percent isobutyl acrylate, referred to below as EBAcnThe second blend contained a mixture of the microcrystalline wax and a copolymer of ethylene and vinyl acetate, and the third blend contained a combination of the microwax and a different copolymer of ethylene and vinyl acetate. The one copolymer of ethylene and vinyl acetate, referred to below as EVA- 1, contained about 65 wt. percent of ethylene and 35 wt. percent of vinyl acetate and had a number average molecular weight of about 2400. A description of the preparation of this copolymer appears in US. Pat. No. 3,600,057, column 5, lines 22-45. The second copolymer of ethylene and vinyl acetate, referred to as EVA-2, had a number average molecular weight of about 1,900 and a mole ratio of ethylene to vinyl acetate of about 4.2 to 1. A description of the preparation of this copolymer appears in Example 1 of allowed copending application Ser. No. 807,966, filed Mar. 17, 1969. See also Canadian Patent 882,194. A principal difference between copolymers EVA-l and EVA-2, is that the latter has about 3 methyl-terminating side branches on the polyethylene backbone per hundred methylene groups in the backbone as compared with about 12 such side branches per hundred backbone methylene groups in the EVA-1 copolymer. All three of the copolymer materials described above have been used in commerce as fuel oil pour point depressants. Each of these was used in this example in the form of a hydrocarbon oil concentrate having about 50 wt. percent active ingredient. The microwax was the same as in Example '1.

The blends referred to were subjected to the low temperature filterability test described in Example 2, the test being run at 5F. The compositions of the blends tested and the test results obtained are given in Table III which follows.

TABLE III Percent Diesel Fuel Through 325 Mesh Screen Additives in 25 See. at 5F.

0.2% Microwax 0.3% EBAcr 0.3% EVA-l .3% EVA-2 .2% Microwax plus .l5% EBAcr .2% Microwax plus .l5% EVA-l N ONUIOO It is to be noted that in contrast to the combinations of microcrystalline wax and pour point depressant additives coming within the scope of this invention, satisfactory low temperature flow of the diesel fuel through a fine screen did not result with combinations of microcrystalline wax and pour point depressant additive outside the scope of the invention.

The combinations of microcrystalline wax and pour point depressants herein described and claimed may constitute the sole additives that are incorporated in the fuel oil compositions, or they can be employed in conjunction with other additives commonly used in distillate fuels, including rust inhibitors, antioxidants, sludge dispersants, demulsifying agents, dyes, haze suppressors, etc.

What is claimed is:

l. A petroleum distillate fuel having a boiling range within the limits of about 250F. and about 700F. which has been improved with respect to its low temperature flow properties by adding thereto:

a. about 0.01 to 2.5 wt. percent of a microcrystalline paraffin wax and b. about 0.005 to 0.5 wt. percent of a fuel-soluble additivef component selected from the group consisti. a halogenated ethylene-containing polymer having a halogen content of from 1 to 40 wt. percent, and

ii. a hydrocarbyl succinamic acid material of the formula:

11 R CH -cox carbon atoms, the other of X and X is of the formula:

wherein n varies from to 1, Y and Y are hydrogen, aliphatic hydrocarbon of from 1 to 30 carbon atoms or oxyaliphatic hydrocarbon of from 1 to 30 carbon atoms, and may be taken together with the nitrogen to which they are attached to form a heterocyclic ring of from five to seven annular members.

2. A fuel composition as defined by claim 1 wherein the proportion of (a) to (b) is within the weight ratio range of from about 20:1 to about 1:20.

3. A fuel composition as defined by claim 1 wherein (b) is a chlorinated homopolymer of ethylene.

4. A fuel composition as defined by claim 1 wherein (b) is a chlorinated copolymer of ethylene and a C to C monoolefin.

5. A fuel composition as defined by claim 1 wherein (b) is a hydrocarbyl succinamic acid material wherein R is derived from mixed C, C cracked wax olefins.

6. A fuel composition as defined by claim 1 wherein said NYY group is derived from amines selected from the group consisting of:

a. di(hydrogenated tallow) amine (C -C b. di(behenyl-arachidyl) amine (C -C c. mixtures of the foregoing.

7. A fuel composition as defined by claim 1 wherein said distillate fuel is a diesel fuel.

8. An additive combination having the property of improving the low temperature filterability of a petroleum distillate fuel when added thereto which comprises:

a. a microcrystalline paraffin wax, and

b. a fuel-soluble additive component selected from the group consisting of:

i. a halogenated ethylene-containing polymer having a halogen content of from 1 to wt. percent, and

ii. a hydrocarbyl succinamic acid material of the formual:

Rgca 00x wherein n varies from 0 to 1, Y and Y are hydro gen, aliphatic hydrocarbon of from 1 to 30 carbon atoms or oxyaliphatic hydrocarbon of from 1 to 30 carbon atoms, and may be taken together with the nitrogen to which they are attached to form a heterocyclic ring of from five to seven annular members, the weight ratio of component (a) to component (b) ranging from about 20:1 to about 1:20. 9. An additive concentrate comprising from about 5 to about 60 wt. percent of the additive combination of claim 8 in an aromatic hydrocarbon solvent. 

1. A PETROLEUM DISTILLATE FUEL HAVING A BOILING RANGE WITHIN THE LIMITS OF ABOUT 250*F AND ABOUT 700*F WHICH HAS BEEN IMPROVED WITH RESPECT TO ITS LOW TEMPERAURE FLOW PROPERTIES BY ADDING THERETO: A. ABOUT 0.01 TO 2.5 WT PERCENT OF A MICROCRYSTALLINE PARAFFIN WAX AND B. ABOUT 0.0005 TO 0.5 WT. PERCENT OF A FUEL-SOLUBLE ADDITIVE COMPONENET SELECTED FROM THE GROUP CONSISTING OF: I. A HALOGENATED ETHYLENE-CONTAINING POLYMER HAVING A HALOGEN CONTENT OF FROM 1 TO 30 WT. PERCENT AND II. A HYDROCARBYL SUCCINAMIC ACID MATERIAL OF THE FORMULA:
 2. A fuel composition as defined by claim 1 wherein the proportion of (a) to (b) is within the weight ratio range of from about 20:1 to about 1:20.
 3. A fuel composition as defined by claim 1 wherein (b) is a chlorinated homopolymer of ethylene.
 4. A fuel composition as defined by claim 1 wherein (b) is a chlorinated copolymer of ethylene and a C3 to C6 monoolefin.
 5. A fuel composition as defined by claim 1 wherein (b) is a hydrocarbyl succinamic Acid material wherein R is derived from mixed C15-C20 cracked wax olefins.
 6. A fuel composition as defined by claim 1 wherein said -NYY1 group is derived from amines selected from the group consisting of: a. di(hydrogenated tallow) amine (C16-C18); b. di(behenyl-arachidyl) amine (C22-C24); c. mixtures of the foregoing.
 7. A fuel composition as defined by claim 1 wherein said distillate fuel is a diesel fuel.
 8. An additive combination having the property of improving the low temperature filterability of a petroleum distillate fuel when added thereto which comprises: a. a microcrystalline paraffin wax, and b. a fuel-soluble additive component selected from the group consisting of: i. a halogenated ethylene-containing polymer having a halogen content of from 1 to 40 wt. percent, and ii. a hydrocarbyl succinamic acid material of the formual:
 9. An additive concentrate comprising from about 5 to about 60 wt. percent of the additive combination of claim 8 in an aromatic hydrocarbon solvent. 